[Haskell] Bug: Safepoint does not work as documented in paper

[Chris Kuklewicz]

One odd problem:  The paper on async exception defines:

safePoint = unblock (return ())

but this simply does not work in my testing.  Ever.  Even using
{-# NOINLINE safePoint #-} or "-Onot"

By comparision, this does work: safepoint = unblock (print "safe")

So how can such a safePoint be written?

-- 
Chris